Operational amplifiers are commonly utilized in electronic circuits to process analog signals. An operational amplifier is often used in integrated circuits that modify analog signals in a particular way, such for example changing amplitudes, filtering frequency components, or performing linear mathematical operations that may include summing with other signals, integration, and differentiation.
Direct current (DC) signals are often used as analog representations of measurements (such as sensed electrical signals from different nodes of a power converter or other circuitries or in other examples sensing/measuring temperature, pressure, flow, weight or motion). Often times, DC current signals are used in preference to DC voltage signals. This is because current signals are substantially equal in magnitude throughout a series circuit loop carrying current from the source (measuring device) to the load (indicator, recorder, or controller), whereas voltage signals in a parallel circuit may vary from one end to the other due to resistive wire losses. Furthermore, current-sensing instruments typically have low impedances, whereas voltage-sensing instruments typically have high impedances; that means that current-sensing instruments generally have greater electrical noise immunity.
An operational transconductance amplifier (OTA) is a well-known amplifier whose differential input voltage produces an output current. Thus, it is a voltage controlled current source (VCCS). Transconductance is an electrical characteristic relating the current through the output of a device to the voltage across the input of a device. That is, conductance is the reciprocal of resistance. Voltage-to-current converting OTAs are utilized in many electronic circuits. For example, OTAs may be used in instrumentation circuitry and in integrated circuit (IC) controllers that are required for operation of switched-mode power converters that power electronic devices such as laptop computers, televisions, etc.
Corresponding reference characters indicate corresponding components throughout the several views of the drawings. Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. Also, common but well-understood elements that are useful or necessary in a commercially feasible embodiment are often not depicted in order to facilitate a less obstructed view of these various disclosed embodiments.